If the ntfs module is compiled into a default Slack9 kernel then you just need to modprobe it:
modprobe ntfs
Then mount the drive:
mkdir /mnt/ntfs
mount -t ntfs /dev/hdx /mnt/ntfs
where /dev/hdx is the device. If you aren't sure which device it is use:
fdisk -l (as root)
To list the partitions. Look for the NTFS partition, that's it ;)